Chandra Deep Field South : Early Black Holes May Have Grown in Fits and Spurts

New research using NASA's Chandra X-ray Observatory and the Sloan Digital Sky Survey (SDSS) suggests supermassive black holes in the early Universe underwent sporadic yet intense periods of growth in the first billion years after the Big Bang as described in our latest press release.
Scientists determined this by comparing theoretical models to data from
the Chandra Deep Field-South (CDF-S), the deepest X-ray image ever
obtained, and other Chandra surveys. This central region of the CDF-S,
where red, green, and blue represent low, medium, and high-energy X-rays.

When material is falling toward a black hole, it becomes heated, and produces large amounts of electromagnetic radiation, including copious X-ray emission. The artist's illustration
in the inset depicts gas falling onto an actively growing black hole
via a disk. X-rays from this disk can penetrate the cocoon of material
surrounding the black hole. Rapidly growing black holes in the very
early Universe should be detectable with Chandra. However, these growing
supermassive black holes have proved to be elusive, with only a few,
yet to be confirmed candidates found in long Chandra observations such
as the CDF-S.

To address this conundrum, a team of researchers examined different
theoretical models and tested them against optical data from the SDSS
and X-ray data from Chandra. Their findings indicate that black hole
feeding during this era may turn on abruptly and last for short periods
of time, which means this growth may be difficult to spot.

The timing of such growth may be key. The authors' model suggests
that 13 billion years ago, about one third of supermassive black holes
may have been accreting enough matter to be detectable. Just 200 million
years earlier — a veritable blip in cosmic time — the number of
potentially detectable black holes is only about 3%. In order to test
this idea further, the researchers suggest that surveys that look at
larger swaths of the sky in X-rays are necessary.

These results recently appeared in a paper in the April 2017 issue of
the Monthly Notices of the Royal Astronomical Society and is available online.
The all-female research team from Italy included Edwige Pezzulli
(University of Rome), Rosa Valiante (INAF), Maria Orofino (Scuola
Normale Superiore), Simona Gallerani (Scuola Normale Superiore), Tullia
Sbarrato (Bicocca University), and Raffaella Schneider (Sapienza
University).